1. Field of the Invention
This invention relates to an image pickup head for an image pickup device adapted to pick up an image of the surface of an object in various fields such as medical fields, industrial fields and the like.
2. Description of the Prior Art
Image pickup devices have been used in various fields which are adapted to abut a surface to be imaged such devices have an image pickup head including built-in light projecting means for illuminating the surface of a section to be observed (hereinafter referred to as an "observed section") of a subject or an object in order to display a magnified image of the surface of the observed section at a monitor image plane. In such image pickup devices, it is essential that illumination of the surface of the observed section is appropriately and accurately carried out.
More particularly, illumination, mainly comprising light, which is vertically projected onto the surface of the observed section of an object against which the image pickup head abuts (hereinafter referred to as "abutment surface") tends to cause the reflection of the light at the abutment surface of the subject to be increased. This results in the image of that portion of the abutment surface at which the reflection of light is increased to appear white on a monitor image plane provided for displaying a magnified image of the abutment surface. This leads to a failure in the satisfactory observation of details of the abutment surface of the object, such as its color, its overall configuration and the like.
Illumination mainly using horizontally projected light, i.e. light which is projected parallel to the abutment surface of the observed section of a subject generally fails to satisfactorily illuminate fine recesses which might exist on the abutment surface. Thus, a finely recessed portion of the abutment surface would appear relatively dark on a monitor image plane for displaying a magnified image of the abutment surface, resulting in an inability to observe fine details in the abutment surface of the subject.
In order to alleviate these problems, the present applicants proposed a light guiding device for illumination suitable for displaying a magnified image of the observed surface of a subject including fine recesses, as disclosed in U.S. patent application Ser. No. 07/362,658 now U.S. Pat. No. 4,930,851.
The proposed light guiding device is adapted to be used with an image pickup head and is constructed so as to eliminate the adverse effect of light reflected on the surface of the observed section of a subject, to permit a three-dimensional magnified image of the surface to be satisfactorily displayed on a monitor image plane. Unfortunately, elimination of light reflected on the observed surface renders the observation of light reflection on the surface substantially impossible.
The forgoing observations will now be considered in connection with the observation of the surface of the skin of the human body. The so-called "shining condition" of the skin such as the complexion and glow of the surface of the skin vary depending upon the health condition of the skin, the degree of aging of the skin and so on. Therefore, the "shining conditions" of the skin are useful in determining the condition of the skin. The detection of the shining condition of the skin for this purpose can be carried out on the basis of the degree of reflection of light at the skin surface. Thus, although it is generally effective and desirable to eliminate the reflection of light at the surface of the observed section of an object in order to observe the object accurately, it is also desirable to detect of light reflected at the surface of the observed section possible.
Furthermore, the image obtained of the observed section of an object, when accompanied by light reflected at the observed section, satisfactorily shows the three-dimensional or stereo configuration of the observed section, whereas the image of the observed section which is free of reflected light effectively indicates the color of the observed section. In the latter case, for example, when the observed section is the skin of a human body, a part of light projected onto the skin penetrates the outer layer of the skin, thereby causing the structure of the outer layer to be clearly observed.
Accordingly, the present applicants have concluded that the substantially simultaneous observation of both an image of the object accompanied by light reflected at the surface of the observed section and an image thereof free of reflected light significantly contributes to the detecting of or observation of cells in which a cancer may have developed, and the like.